This invention relates to devices for loading bone anchors into bone-anchor insertion devices and methods of using such bone-anchor loading devices.
Bone anchors are used in surgical procedures to create attachment sites for surgical implants such as sutures, patches, or slings. Bone anchors may be divided into two general categories: bone anchors that require pre-drilling and self-tapping bone anchors. Self-tapping bone anchors are more efficient than those requiring pre-drilling because the use of self-tapping bone anchors collapses three steps (i.e., pre-drilling into bone, locating the pre-drilled hole, and inserting the bone anchor into the pre-drilled hole) into a single step.
Self-tapping bone anchors generally include a sharp leading tip, an inserting feature, a retaining feature, and a suture attachment site. Some bone anchors are configured as conical screws in which the inserting and retaining functions are served by threading which covers the entire shank beginning at a sharp distal tip. Other bone anchors are configured as drill bits in which the inserting function is served by a fluted cutting surface terminating in a sharp leading tip at the distal end of the shank; the retaining function is accomplished by threading located at the proximal end of the shank. Bone anchors configured as screws or drill bits may be introduced into bone using a rotary bone-anchor inserter, e.g., a drill.
Other self-tapping bone anchors are configured without any threading. In such bone anchors a sharp leading tip, such as a biomet crown, serves the insertion function and wings positioned on the shank serve the retaining function. Such bone anchors may be introduced into bone by applying linear force upon the bone anchor using a press-in type bone-anchor inserter device.
Many bone-anchor inserter devices are delivered to the surgeon in sterile packaging with the bone anchor preloaded and, optionally, the suture preattached. In surgical procedures requiring more than one bone anchor, the surgeon may reload the bone-anchor inserter device manually.
Manual loading of a bone anchor into a bone-anchor inserter may be accomplished by pinching the bone anchor between two fingers at the sharp distal end of the shank, aligning the shaft of the bone anchor with the mount of a bone-anchor inserter, and pushing the bone anchor into the bone anchor mount. This is an awkward and time-consuming procedure, which presents risks to both the patient and the surgeon. One potential risk is that the surgeon may drop the small bone anchor while attempting to manipulate it. A more serious risk is that the surgeon may puncture his or her surgical gloves and/or skin, and thus cause injury to the surgeon and breach the sterility of the bone anchor, the bone-anchor inserter, and/or the operating area.
One known bone-anchor loading device engages the bone anchor by the distal end of the shank, which can dull the bone anchor threads or the fluted cutting edges located on the distal end of the shank, making insertion of the bone anchor into the bone difficult. Likewise, this bone-anchor loading device deploys the bone anchor into the bone-anchor inserter by applying linear force upon the sharp distal tip of the bone anchor, which may damage the distal tip and thereby complicate insertion of the anchor into the bone. Furthermore, very little force is required to deploy a bone anchor from this bone-anchor loading device and, therefore, the bone anchor may deploy before the shaft of the bone anchor is properly seated in the mount of the inserter.
Accordingly, there is a need for a device and method of loading a bone anchor into a bone-anchor inserter that is safe and efficient. There is a further need for a device and method of loading a bone anchor into a bone-anchor inserter that does not apply damaging forces upon the leading point, the distal cutting edges and/or the distal threads of the bone anchor.
The present invention provides a bone-anchor loading device useful for efficiently and safely loading a bone anchor into a bone-anchor inserter without applying force on the leading tip, the distal cutting edges, and/or the distal threads of a bone anchor. The device is conveniently used, reliable, and can be dimensionally matched to standard bone-anchor inserters to facilitate interoperation therewith.
In some embodiments, the bone-anchor loading device comprises a main body including a gripping portion, a bone-anchor receiving member, and an elongated sleeve. The elongated sleeve may be coaxially disposed over the bone-anchor receiving member and configured for slidable translation thereover. The bone-anchor loading device may also include an interference fitting that engages when the sleeve is translated to an interference position with respect to the main body. The engagement between the sleeve and bone-anchor receiving member causes the receiver fitting to releasably secure a bone anchor.
Some embodiments of the invention may also include an alignment feature to maintain a fixed angular orientation between the receiving member and the sleeve. Accordingly, the bone-anchor loading device may further comprise an alignment recess formed in one of the sleeve and the anchor-receiving member, and an alignment-recess mate projecting from the other of the sleeve and the anchor-receiving member. The alignment recess mate may be configured to slidably couple with the recess and prevents rotation between the sleeve and the receiving member. The alignment recess may have an axial length along the longitudinal axis determining at least one stop position. The stop position may limit travel of the sleeve relative to the anchor-receiving member when the sleeve is extended relative to the anchor-receiving member and/or when the sleeve is retracted relative to the anchor-receiving member.
In some embodiments, the alignment recess may be one or more slots extending fully through one of the sleeve and the anchor-receiving member, and the alignment recess mate may be a guide pin secured to the other of the sleeve and the anchor-receiving member. In one preferred embodiment, the alignment recess mate is a guide pin secured to the elongate bone-anchor receiving member, the sleeve includes a pair of opposing slots, and the guide pin has a length greater than the diameter of the receiving member such that each of the opposing slots travels along the guide pin.
In some alternative embodiments, the elongated bone-anchor receiving member and the elongated sleeve have off-round profiles.
In some embodiments, the gripping portion may comprise a pair opposing flat surfaces that may, optionally, include raised ridges or other texturing to provide a firm gripping surface.
In one embodiment, the engagement between the sleeve and the anchor-receiving member applies tension on the receiver fitting, thereby causing the receiver fitting to engage a bone anchor loaded in the receiver fitting. In a preferred embodiment, the retention forces are applied only to the proximal end of the bone-anchor shank. For example, the receiver fitting may be a split conical recess located at the distal end of the receiver fitting and adapted to receive the distal portion of a conical bone anchor.
In preferred embodiments, the receiver fitting comprises deformable material and an interference fit results from inward radial force being applied upon the receiver fitting. The inward radial force may result from an enlarged outer diameter on the distal end of the receiver fitting contacting a narrowed inner diameter on the proximal end of the sleeve. In preferred embodiments, the anchor-receiving member and the sleeve cooperate to release the bone anchor without exerting force on the distal end of the bone anchor including, the sharp leading tip, and where applicable, the distal cutting surface and/or the distal threading of the bone anchor.
The bone-anchor loading device may, optionally, include at least one wing disposed on the outer surface of the sleeve, which is configured to facilitate positioning the sleeve and receiving member into the interference position when a bone anchor is positioned within the deformable receiver member. In some embodiments, the wing may be in the form of a collar disposed on the outer surface of the sleeve. In other embodiments, a pair of wings may be oppositely disposed on the outer surface of the sleeve.
In some embodiments, the distal end of the sleeve is transparent to permit visualization of at least the shaft of a bone anchor loaded in the bone-anchor loading device.
In some embodiments, the bone-anchor loading device is preloaded with a bone anchor, and optionally, a preattached suture.
In another aspect, the invention features methods of loading a bone anchor into a bone-anchor inserter. Embodiments of this aspect of the invention include the following features.
In one embodiment, the method of the invention comprises the steps of providing a bone-anchor loading device configured to releasably retain a bone anchor by the distal end of the bone-anchor shank; loading a bone anchor into the loading device; causing retention of the bone anchor therein; coupling the loading device with the inserter so as to seat the bone anchor within the inserter; and operating the loading device to release the seated bone anchor into the inserter.
The bone-anchor loading device may comprise a main body including a gripping portion and, projecting therefrom, an elongated bone-anchor receiving member having a receiver fitting at a distal end thereof; an elongated sleeve coaxially disposed over the anchor-receiving member and configured for slidable translation thereover; and an interference fitting causing engagement between the sleeve and the anchor-receiving member when the sleeve is translated to an interference position with respect to the main body, the engagement further causing the receiver fitting to deform to releasably secure a bone anchor.
In some embodiments, the operating step comprises pushing the body of the bone-anchor loading device toward the bone-anchor inserter. The operating step may further comprise forcing the distal end of the sleeve proximally toward the gripping portion of the main body to thereby relieve the interference fit and release the bone anchor from the bone-anchor loading device.
In preferred embodiments, force is not applied upon a leading tip of the bone anchor during the loading and the operating steps, nor is force applied upon a cutting surface or the distal threading of the bone anchor during the loading and the operating steps.
The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.